JPH0453060A - Mirrored disk device - Google Patents

Abstract

PURPOSE:To synchronize rotary phases, to increase access speed and to secure maintenance by controlling the rotation of two disks by one clock. CONSTITUTION:In a normal state, the same clock is inputted from a rotation control clock generating means 1 to both disk devices and applied through respective clock monitoring means and switching means to rotation control means, and the rotation of a disk 10 (or 11) is synchronously controlled. When the rotation control clock generating means is defective, when a cable 14 is disconnected or when faults are generated in clock monitoring means 2 and 3, the respective clock switching means detect signals showing the absence of the clock and since the clock of a shelf-clock generating means 4 (or 5) is selected, there is no problem in the operation. On the other hand, since a circuit to inspect and compare the output clock of the clock switching means is mounted or the output clock is periodically checked, the fault is easily detected.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to improving the performance of a dual disk (hereinafter referred to as mirrored disk) device used as a highly reliable auxiliary storage device in a computer system.

<Prior Art> FIG. 2 shows an example of the configuration of a conventional mirrored disk. A host H is connected to disks A (active side) and disk B (standby side).

If the standby disk B fails for some reason, only the active disk A will operate. vice versa,
When the active disk A fails, the standby disk B is switched to the active disk.

There are several operating side management methods, including the following management methods.

■The operating side reads/writes (Read/Write)
, the standby side is write only, and write accesses are performed simultaneously.

■The active side and the standby side read/write in the same way, and access both read and write at the same time. At this time, the read on the standby side is for the purpose of failure detection, and the host uses the data on the active side.

<Problem to be solved by the invention> However, in such a mirrored disk device, two
At present, when writing or reading/writing to two disks at the same time, the rotational phases of each disk are not synchronized, and the rotational waiting time is different for each disk, resulting in the problem of the disk having a slower access time. Ta.

On the other hand, in disk driving, etc., where multiple disks are logically regarded as one disk, a rotation period is achieved, but even if one disk fails, it is considered as a failure of the entire disk, and mirrored disks Maintainability and reliability could not be achieved.

The present invention has been made in view of the above points, and an object thereof is to provide a mirrored disk device that improves the access speed of mirrored disks.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides a rotation control clock generating means for generating a clock for disk rotation control which can be connected to a disk device from the outside. The two disk devices have a clock monitoring means for receiving the clock from the rotation clock generation means and detecting whether or not there is an abnormality in the clock, and a clock monitoring means built in the disk device main body for generating a clock for rotation control. Based on the detection results from the internal clock generation means and the clock monitoring means, if there is no abnormality in the rotation control clock from the outside, the external clock is selected, and if there is an abnormality, the clock from the internal clock generation means is selected. The present invention is characterized in that it consists of two disk devices, each comprising a switching means for selecting the clock of the switching means, and a rotation control means for controlling the rotation of the disk in response to the clock output from the switching means.

In the present invention, the rotation phases of two disks are synchronized by controlling the rotation of two disks using a clock from one rotation control clock generating means.

Note that if an abnormality occurs in the externally applied clock, the rotation of the disk is controlled by the clock from the internal clock generating means. In this case, it is not possible to synchronize the rotational phase, but the failure can be easily resolved through maintenance, and the rotational phase can be immediately synchronized using an external clock.

<Example> The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a configuration diagram showing an embodiment of a mirrored disk device according to the present invention. In the figure, the part 2 surrounded by the broken line
0 is a circuit that executes rotation control of the mirrored disk, and the part 3o surrounded by double lines is the main body of the disk device that can be disconnected for maintenance purposes in the event of a disk failure;
The two disk devices have the same configuration.

In FIG. 1, 1 is a rotation control clock generation means, 2 and 3 are clock monitoring means, 4 and 5 are internal clock generation means, 6 and 7 are switching means, 8 and 9 are rotation control means, 10 and 1] is disk, 12 and ]
3 is an interface bus for connecting with a host (not shown).

The rotation control clock generating means 1 generates a rotation control clock suitable for the disk device. This clock is input to the clock monitoring means 2, 3 and the switching means 6.7, respectively.

The clock switching means 6 (or 7) monitors whether the clock from the rotation control clock generating means 1 is output within a certain period, and if the clock has stopped, changes the clock generation within its own device. Switch to the clock from means 4 (or 5).

The output of the switching means 6 (or 7) is given to the rotation control means 8 (or 9).

The rotation of the disk [0 (or 1]) is controlled by a clock provided by the rotation control means 8 (or 9).

disk] 0 (or 1) is interface bus 1
2 (or 13) to a host (not shown), and is accessible from the host.

In such a configuration, under normal conditions, that is, when there is no hardware failure, the same clock from the rotation control clock generation means 1 is input to both disk drives, and the clock monitoring means 2 (or 3) and switching means 6
(or 7) to the rotation control means 8 (or 9), and the rotation of the disk 10 (or 11) is synchronously controlled. As a result, the rotations of the two disks can be synchronized, and there will be no deviation in rotational phase between the disks.

Next, a case where the hardware breaks down for some reason will be explained. Note that mirrored disks cannot normally guarantee operation against double failures or more, so only the operation and management in the case of a single failure will be described here.

■If a failure occurs in the rotation control clock generation means], a disconnection in the external clock supply cable 4, or a failure in the clock monitoring means 2 or 3, in this case, the clock is switched off by the clock switching means 6 (or 7). It is detected that no input is received within a certain period, and in this case, switching is performed to select the clock from the clock generating means 4 (or 5) within the own device.

However, in this case, as with general mirrored disks, the rotations of the two disks cannot be synchronized, and there is either a performance drop or no operational problem.

Incidentally, such failures can be easily detected by implementing a circuit that inspects and compares the output clock of the clock switching means 6.7 or by performing periodic inspections, and if maintenance is carried out at that point, the problem can be solved. Solvable.

■When there is a failure such that the clock is not output from the clock switching means 6 (or 7), or when there is an abnormality in the rotation control means 8 (or) or the disk 10 (or) 1. In this case, access to the disk device concerned is Therefore, the host can detect an abnormality in the disk device, and if maintenance is performed at that point, the failure can be resolved.

As is clear from the above description, according to the present invention, two disks can be rotated synchronously, and a mirrored disk without rotational phase shift can be realized. As a result of eliminating the rotational phase shift, there is no decrease in performance due to differences in rotational wait times as shown in the conventional example.

<Effects of the Invention> As described above in detail, according to the present invention, there is no rotational phase shift, and it becomes possible to access a mirrored disk with the same performance as normal disk access.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a mirrored disk device according to the present invention, and FIG. 2 is a diagram showing an example of a conventional mirrored disk connection. 1...Rotation control clock generation means 2.3...Clock monitoring means 4.5...Internal clock generation means 6.7...Switching means 8.9...Rotation control means 1.0. 1.1... Disk

Claims (1)

[Scope of Claims] Rotation control clock generation means for generating a clock for disk rotation control externally applied to a disk device; and two disk devices having the same configuration, each of which receives a clock from the rotation clock generation means. A clock monitoring means for detecting the presence or absence of a clock abnormality, an internal clock generation means built into the disk device main body for generating a clock for rotation control, and an external rotation control based on the detection result of the clock monitoring means. A switching means that selects an external clock when there is no abnormality in the clock, and selects a clock from a clock generation means within the device when there is an abnormality, and a switching means that selects a clock from the clock generation means in the device when there is an abnormality in the clock; A mirrored disk device comprising two disk devices each comprising a rotation control means for controlling rotation.